Okay, for many the fact that this typewriter plays Zork on paper instead of a CRT is the fascinating part of this hack. But we love the implementation that makes the keys of the device an input and output.
The electric typewriter has been fitted with a solenoid for each key (wow, that’s a lot of work). In the image above you can see they are housed on plywood platforms behind the typewriter and connect using a piece of mono-filament fishing line. This flexible connection means the solenoids have no adverse effect when you want to do the typing instead of the Arduino which drives the solenoids. [Johnathan M. Guberman] took advantage of this, adding a resistor for each key. When depressed the key completes a circuit with the resistor, acting as the input. In this way, you can play Zork with a piece of paper as the monitor, typing for the input, and watching the typewriter magically pound out responses. See it happen after the break.